Large area light panel and screen

ABSTRACT

Embodiments of a panel lighting apparatus and methods of its manufacture are described. In one embodiment, the apparatus can include a light source, an at least partially transparent panel comprising a planar front surface and a planar back surface, the panel disposed in conjunction with the light source such that light from the light source is input into at least one edge of the panel and guided therein, and a plurality of light extraction dots disposed on the planar back surface, the plurality of light extraction dots configured to reflect light incident on the planar back surface and extract light from the light source propagating in the panel through the planar front surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 12/482,294, filed Jun. 10, 2009, which claims the benefit of U.S.Provisional Application No. 61/144,352 filed on Jan. 13, 2009, both ofwhich are hereby expressly incorporated by reference in theirentireties.

BACKGROUND

1. Field of the Invention

The invention relates to the field of lighting, and in particular, lightextraction in light panels and privacy displays.

2. Description of the Related Art

A variety of architectural lighting configurations are utilized toprovide artificial illumination in a wide variety of indoor and/oroutdoor locations. Such configurations can include fixed and portablearchitectural lighting. Various configurations can employ technologiessuch as incandescent, fluorescent, and/or light emitting diode basedlight sources.

One type of architectural lighting configuration can be referred togenerally as panel lighting. Panel lights may include, for example,fluorescent lighting in a light box behind a plastic lenticular panel.Panel lighting is often configured as planar and square or rectangularand having width and length dimensions significantly greater than athickness dimension. While the thickness of panel lighting is generallysignificantly less than corresponding width and length dimensions, it isfrequently the case that the thickness of existing panel lighting forceslimitations in installation and use. Display front and backlighttechniques can be applied to large area (such as 4′×8′) flat panellighting.

One specific type of panel lighting is flat panel lighting. Flat panellights are commonly found in flat panel display applications, whichinclude a transparent panel designed to provide illumination from itsplanar surface. Light is provided into the panel from a light source(e.g., LEDs or a CCFL lamp), which may be positioned along one or moreedges of the panel. Light travels throughout the panel, staying withinthe panel due to total internal reflection at its front planar surfaceand back planar surface. At some places on the panel, light may bedirected out of the panel by an extraction feature.

Flat light panels can be sized for luminaire or architecturalapplications. For architectural applications a panel may be about 4′×8′,or made of tiles of smaller dimensions. Some embodiments include two ormore flat light panels adjacently disposed. Thus, flat panel lights canbe applied to large areas. Flat panel lights can be used as a luminaireor as a partially transparent light panel and screen. For example, aflat panel light may be used as a privacy screen. The panel can beglass, polymer such as acrylic, polyethylene terephthalate,polycarbonate etc. A 4′×8′ panel may require a thickness of about 0.25″or greater to allow adequate transmission of light along its width, whenilluminated from two edges.

In existing panel designs, light extraction features are often groovesor other features cut into the surface of the panel. However, thesemachined or embossed features are costly and do not allow forflexibility in design.

SUMMARY

The system, method, and devices of the invention each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention, its moreprominent features will now be discussed briefly. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description of Certain Embodiments,” one will understand howthe features of this invention provide advantages over other lightingdevices.

Certain embodiments of the invention include light extraction dotspainted or printed onto a light panel privacy screen. Privacy screenpanels can include light extraction dots that, when illuminated, obscureviewing objects behind the screen. For ease of manufacturing the dotscan be printed onto the panel. In some embodiments, the panel isconfigured with dots in a configuration to decouple the opticalcharacteristics of light entering a front surface of the panel andtransmitted through the panel and out the back surface, and lightextracted out of the front surface. In other words, the panel can beconfigured to have a different visual (or optical) effect when the panelis viewed from either its front or back surface.

According to one embodiment, the invention comprises a lightingapparatus comprising a light source, an at least partially transparentpanel comprising a planar back surface and a planar front surface, thepanel disposed in conjunction with the light source such that light fromthe light source is input into at least one edge of the panel andpropagates therein and a plurality of light extraction features disposedon the panel back surface, the plurality of light extraction featuresconfigured to reflect light incident on the panel back surface andextract light from the light source propagating in the panel through thepanel front surface. In one aspect, the at least one light extractionfeature comprises an inner layer disposed near the panel back surfaceand an outer layer disposed at least partially on the inner layer. Inanother aspect, part of the outer layer is disposed on the panel backsurface. In one example, the outer layer may comprise a first coloredmaterial that reflects light of a first color and the inner layer maycomprise a second colored material that reflects light of a secondcolor, the first color may be different from the second color or thesame. In one example, the first color is white. In another aspect, areflector is disposed adjacent to the planar front surface and/or adiffuser is disposed adjacent the panel back surface. In one example,the panel may comprise glass, polymer, polycarbonate, or polyethyleneterephthalate.

In another embodiment, the lighting apparatus may comprise an isolationlayer disposed between at least one, or at least a portion of one, lightextraction feature and the panel back surface and the isolation layermay have a refractive index that is less than the refractive index ofthe panel. In one example, the isolation layer may include two or moresections with each section disposed between at least a portion of alight extraction feature and the panel such that the isolation layer isnot disposed between a portion of one light extraction feature and thepanel. In another example, the isolation layer may be disposed betweennon-extraction features and the panel as well as between lightextraction features and the panel. In another aspect, an isolation layermay be disposed between a portion of at least one light extractionfeature and the back panel surface such that the isolation layer is notdisposed between another portion of the at least one light extractionfeature and the back panel surface. In one example, at least one lightextraction feature may be disposed on the panel back surface without anisolation layer therebetween.

In one embodiment, the light extraction features comprise at least onelight extraction dot and the dot may comprise material that can beprinted or painted onto the panel back surface. In one example, the dotmaterial may comprise ink or ink with an ink binder having a refractiveindex equal to or less than the refractive index of the panel. Inanother aspect, the dot material may comprise diffusive particles. Inone example, the light extraction features comprise a binder materialand a plurality of diffusive particles. In one aspect, the diffusiveparticles comprise titanium dioxide or zinc oxide. In another example,the refractive index of the diffusive particles is greater than therefractive index of the binder material.

In another aspect, the lighting apparatus may comprise at least onesecondary dot disposed on the panel back surface and the at least onesecondary dots may extract less light than the plurality of lightextraction dots. In one example, the light extraction dots and secondarydots may be disposed together in a pattern with uniform spacing. Inanother aspect, the light extraction dots may be disposed upon at leastone side of the panel and patterned to uniformly or non-uniformlyextract at least some light from the panel. In another example, thelight extraction characteristic is the ink binder refractive index orthe number of diffusive particles. In one aspect, the lighting apparatusmay include a group of light extraction features on the panel frontsurface and they may be disposed in a uniform or non-uniform pattern.The light extraction features disposed on the panel front surface maycomprise light extraction features of differing sizes. In one example,at least two of the light extraction features on the front may comprisedots with different diameters, thicknesses, refractive indices, ordifferent numbers of diffusive particles. In another example, thelighting apparatus may include a group of light extraction features onthe panel front surface and a group of light extraction features on thepanel back surface with at least one light extraction feature on theback surface comprising a dot with a different diameter, thickness,refractive index, or number of diffusive particles than a lightextraction dot on the front surface. In another aspect, the lightingapparatus may include a group of light extraction features on one sideof the panel. The light extraction features may comprise dots and byvarying the opaqueness of the dots, light may be extracted only towardone side, or both sides, of the lighting apparatus.

In another aspect, the light source in the lighting apparatus maycomprise a light emitting diode, a fluorescent light, a plurality oflight emitting diodes disposed with respect to the panel such that lightemitted from the diodes is injected at one or more edges of the panel,or a plurality of light emitting diodes disposed along two oppositeedges of the panel.

According to another embodiment, the invention comprises a method ofmanufacturing a lighting apparatus comprising optically coupling a lightsource to an at least partially transparent panel comprising a planarback surface and a planar front surface, the panel disposed inconjunction with the light source such that light from the light sourceis input into at least one edge of the panel and guided therein andprinting a plurality of light extraction features on the panel backsurface, the plurality of light extraction features configured toreflect light incident on the panel back surface and extract light fromthe light source through the panel front surface. In another aspect, theplurality of light extraction features are printed on the panel using anink jet printer or by screen printing.

According to another embodiment, the invention comprises a lightingapparatus comprising an at least partially transparent panel comprisinga planar back surface and a planar front surface for propagating lighttherebetween and a plurality of light extraction dots disposed on thepanel back surface, each light extraction feature comprising an innerlayer disposed on the panel back surface and outer layer disposed atleast partially on the inner layer, the inner and outer layer having adifferent light reflective characteristic. In one aspect, the innerlayer may reflect light of a first color and the outer layer may reflectlight of a different second color.

In another embodiment, the invention comprises a light apparatuscomprising a light source, an at least partially transparent panelcomprising a planar back surface and a planar front surface andconfigured to receive light provided from the light source through anedge of the panel and propagate the light in the panel and a pluralityof light extraction dots disposed on the panel front surface, theplurality of light extraction dots configured to extract lightpropagating in the panel through the panel back surface. In one aspect,the light extraction dots comprise diffusive particles. In one example,the light extraction dots are configured to extract light propagating inthe panel through the panel front surface. In one aspect, the lightextracted through the panel front surface may be of a different colorthan the light extracted through the panel back surface. In anotherexample, the light extraction dots are configured to extract coloredlight through the panel back surface different than the color of lightprovided by the light source.

According to another embodiment, the invention comprises a lightapparatus comprising an at least partially transparent panel comprisinga planar front surface and a planar back surface and configured toreceive light provided from a light source through an edge of the paneland propagate the light within the panel and a film bonded to the panelback surface, the film having a plurality of light extraction dotsdisposed thereon such that the film is disposed between the panel backsurface and the plurality of light extraction dots, the plurality oflight extraction dots configured to extract light propagating in thepanel through the panel front surface. In one aspect, the lightapparatus may comprise a light source and/or an adhesive disposedbetween the film and the panel. In one aspect, the adhesive is apressure sensitive adhesive. In one example, the light extraction dotscomprise diffusive particles and/or are configured to extract lightpropagating in the panel through the panel back surface. In anotherexample, the light extraction features are configured to extract coloredlight through the panel front surface different than the color of lightprovided by the light source. In one embodiment, the light extractionfeatures may extract a different color through the panel back surfacethan the panel front surface.

According to another embodiment, the invention comprises a method ofmanufacturing a lighting apparatus comprising printing a plurality oflight extraction dots onto a sheet and bonding the sheet to a surface ofan at least partially transparent light panel having a front and backsurface such that the sheet is disposed between the plurality of dotsand the panel. In one aspect, the bonding comprises attaching the sheetto the panel using an adhesive having an equal or lower refractive indexthan the refractive index of the panel such that the light extractiondots are operable to extract light propagating between the panel frontand back surface. In another aspect, the bonding comprises attaching thesheet to the panel using heat and/or pressure. In one example, the sheetcomprises a clear amorphous thermoplastic or glycol-modifiedpolyethylene terephthalate (“PETG”).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a privacy screen position in front of anobject (flowers) where the light source of the privacy screen is eitheroff or decreased thus, allowing a clear view of the object.

FIG. 2 is a front view of the privacy screen of FIG. 1 where a lightsource provides light into the privacy screen and at least a portion ofthe light is emitted from the front of the privacy screen changing theappearance of the object as viewed through the privacy screen.

FIG. 3 is a front view of a privacy screen schematically illustratingone embodiment having machined light extraction features.

FIG. 4 is an edge view of a privacy screen schematically illustratingone embodiment of a privacy screen having machined light extractionfeatures.

FIG. 5 is a front view schematically illustrating one embodiment of aprivacy screen having printed light extraction features.

FIG. 6 is an edge view schematically illustrating one embodiment of aprivacy screen having printed light extraction features.

FIG. 7 is a front view schematically illustrating a privacy screenhaving light extraction features printed on the front and/or backsurface in a uniform pattern.

FIG. 8 is a front view of a privacy panel illustrating an embodimentwhere light extraction features smaller than those shown in FIG. 7 areprinted on a front and/or back surface in a uniform pattern.

FIG. 9 is a front view of a privacy panel schematically illustrating anembodiment having light extraction features of various sizes printed onthe front and/or back surfaces in a non-uniform pattern.

FIG. 10 is an edge view schematically illustrating one embodiment of aprivacy screen having dot light extraction feature printed on a surfaceof the panel.

FIG. 11 is an edge view schematically illustrating one embodiment of aprivacy screen that is configured to emit light out of its front andback surfaces.

FIG. 12 is a close-up edge view of a privacy screen schematicallyillustrating one embodiment of a dot light extraction feature.

FIG. 13 is a close-up edge view schematically illustrating oneembodiment of a dot light extraction feature having a greater particledensity than the embodiment shown in FIG. 12.

FIG. 14 is an edge view schematically illustrating an embodiment of aprivacy screen having dot light extraction features of various sizesprinted on the front and back surfaces.

FIG. 15 is an edge view schematically illustrating one embodiment of aprivacy screen having isolating layers disposed between portions of dotlight extraction features and the transparent panel.

FIG. 16 is a front view schematically illustrating an embodiment of aprivacy screen having light extraction dots printed onto the transparentpanel and non-light extraction dots disposed on the transparent panel.

FIG. 17 is an edge view schematically illustrating an embodiment of aprivacy screen having multi-layer light extraction dots disposed on thetransparent panel.

FIG. 18 is a front view schematically illustrating one embodiment of aprivacy screen having colored dot and white dot light extractionfeatures printed on the transparent panel.

FIG. 19 is an edge view schematically illustrating an embodiment of aprivacy screen having a reflector disposed near the transparent panel.

FIG. 20 is an edge view schematically illustrating an embodiment of aprivacy screen having a diffuser disposed near the transparent panel.

FIG. 21 is an edge view schematically illustrating an embodiment of aprivacy screen with a film adhered to the transparent panel where thefilm has light extraction features disposed on the non-adhesive side ofthe film.

FIG. 22 is a block diagram schematically illustrating an embodiment of amethod of manufacturing a lighting apparatus.

FIG. 23 is a block diagram schematically illustrating an embodiment of amethod of manufacturing a lighting apparatus.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description is directed to certain specificembodiments of the invention. However, the invention can be embodied ina multitude of different ways. For example, features included in aprivacy screen embodiment may also be included in a luminaireembodiment. In this description, reference is made to the drawingswherein like parts are designated with like numerals throughout.

Privacy screen panels (sometimes referred to herein as “panels”) mayinclude numerous light extraction features cut or embossed into one orboth of the planar surfaces of the panel. The light extraction featuresmay include, for example, grooves, puts, or prismatic features which areformed as part of the panel. However, manufacturing such features can becostly and their use may limit flexibility in design. Alternatively,“dot” light extraction features may be placed (e.g., printed) onto oneor both planar surfaces of a panel to extract light in a desired way.Light extraction dots (“dots”) as used herein, is a broad term thatrefers to a mass of material that is configured to have certain opticalcharacteristics, and that is placed on a surface of the privacy screen.In various applications, dots may be configured in various sizes (e.g.,length, width, and height), shapes, colors, and compositions to exhibitdesired optical characteristics. Some examples of dot cross-sectionalshapes includes circles, ovals, generally curvilinear shapes, squares,rectangles, triangles, generally polygonal shapes, and irregular shapes.In a configuration that includes numerous dots, the dots may be disposedin a uniform pattern or another pattern to produce a desired opticaleffect, and each dot may each be about the same size or the dots canvary in size.

For example, privacy screen panels can include light extraction dotsthat, when illuminated by a light source that provides light into one ormore edges of a panel, obscure viewing objects behind the screen. Forease of manufacturing, the dots can be printed onto any surface of thepanel. In some embodiments, light extraction dots are printed on aseparate sheet which is then bonded or laminated to a transparent panelforming the privacy screen. In some embodiments, the panel can beconfigured to have a different visual (or optical) effect when the panelis viewed from either its front or back surface. Such embodiments areparticularly useful for privacy screens. In other embodiments, the panelcan be designed to extract light out of both the front and back sides ofthe panel and the panel can then act as a privacy screen in bothdirections.

Privacy screen panels configured with light extraction features (e.g.,printed dots) and a light source can be used as a light “shutter,”operating to allow an object to be seen through the privacy screen whenthe light source is dimmed or off (e.g., an “open” shutterconfiguration). When the light source is “on,” it provides light intothe privacy screen panel where the light propagates between the surfacesof the privacy screen panel by total internal reflection. When the lightsource is on, various embodiments of extraction dots can be used toextract light out of the panel towards a viewer. The increased level ofextracted light obscures the view of an object located behind the panel,e.g., on the opposite side of the panel from the viewer, thus forming a“closed” shutter configuration. By actuating the light source whendesired, or at certain triggering events, the privacy screen “shutter”can be opened or closed. For example, a door comprising a privacy screenas a light shutter could be configured to actuate the light “closing”the shutter when the door is closed (or when the door locks, or inresponse to a switch) thus providing privacy, only when needed. In someembodiments, the privacy screen is configured to appear a certain colorwhen the shutter is closed such that a viewer sees a colored panelinstead of object through the panel. Privacy screens configured as lightshutters can also be implemented instead of windows (e.g., in commercialoffices) to provide privacy with an aesthetically pleasing appearanceobviating mechanical blinds or shutters. Such light shutters can use anyof the embodiments described below, or combinations of theseembodiments, where actuating the light source fully or partiallyobscures the privacy screen to provide the desired level of privacy.

FIG. 1 shows a front schematic view of one embodiment of a privacyscreen 100. The privacy screen 100 includes a panel 101 and one or morelight sources 103 disposed along left and right edges (relative to thepanel 101 illustrated in FIG. 1) of the panel 101. The panel 101comprises a first (or front) planar side, a second (or back) planarside, a top edge, a bottom edge, a left-side edge, and a right-sideedge. The “front” and “back” “sides” are also referred to herein as the“front surface” and the “back surface”, respectively. The light sources103 may be placed on one or more edges of the panel 101, including allfour edges. The front planar side is opposite the back planar side. Forclarity of description, the embodiments will generally be described inrelation to a front side and a rear side, where the front planar side isreferenced as pointing out of the page, unless stated differently, andis also described as being closer to a viewer than the back planar side.However, one of skill in the art will appreciate that the panel can bedisposed in any direction during use, including flipped front to back;accordingly every embodiment and example described herein with referenceto the front surface can also be implemented on the back surface andvise-versa.

In some embodiments, the front planar side and back planar side may haveapproximately the same surface area. However, it is possible they couldbe different in size, for example, in embodiments where the edges areslanted (e.g., not perpendicular to the front and back surfaces). Thefront planar side and back planar side may be dimensioned to mask atleast a portion of a particular object 105 when the privacy screen 100is placed in front of the object. For example, the front planar side andback planar side may be 4′×8′. When the light sources 103 are dimmed orturned off the transparency of the panel is affected by the opticalproperties of light extraction features present on the transparent panelthat affect ambient light; accordingly, the panel 101 may appearpartially transparent. As shown in FIG. 2, when the light sources 103are turned on, the panel 101 appears bright and opaque. Thus, a privacyscreen 100 may be used to shield an object 105 or the area behind theprivacy screen 100 from a viewer. When lit, the panel 101 can contributeto the level of apparent transparency of the screen 100. If the panel101 is brightly lit by the light sources 103, objects behind the screen100 may be hidden from a viewer as the contrast of the scene viewedthrough the panel 101 is reduced. The light extracted from the paneltoward the viewer can be altered by varying the output of the lightsources 103. In some embodiments, the luminance of the light extractedtowards a viewer through the panel 101 is approximately 100 timesgreater than the luminance of light emitted from or being reflected fromthe object 105, viewed through panel 101 and the object is completelyobscured such that the viewer will no longer be able to distinguish theobject due to limitations of human vision. In other embodiments, theluminance of light extracted towards a viewer is approximately 50 timesgreater than the luminance of light emitted from or reflected from theobject 105 through the panel 101 and the object is only partiallyobscured. Thus, a panel 101 may be used to completely or partiallyobscure an object 105 to one or more viewers. In some embodiments, theobject behind screen 101 may be moving, in which case the ratio ofluminance may need to be higher, due to the ability of human vision todetect moving objects more easily than static objects.

The amount of light required to completely or partially obscure anobject 105 to a viewer depends on the relative difference of luminancebetween the object 105 and the panel 101, when the object is viewedthrough the panel 101. The luminance of the object 105 depends onambient and artificial light incident on the object 105, and any lossesthrough the panel 101. The luminance of the panel 101 is affected bylight extracted from the panel. In one example, an object in the familyroom in a standard home may have an apparent luminance of about 15candela per square meter (cd/m²) requiring a panel 101 luminance ofapproximately 1,500 or more cd/m² in order to completely obscure theobject behind the panel. In another example, an object 105 in an officehas an apparent luminance of about 50 cd/m² and a panel 101 luminance ofapproximately 5,000 or more cd/m² is required to completely obscure theobject behind the panel.

The form, dimension, and distribution of the light turning/extractionfeatures (not shown) impact the lit and unlit visual appearance of theprivacy screen 100. Design of these features and their configuration onthe panel 100 can be made to optimize both the lit and unlit state ofthe screen 100. Printed dots make an effective light extraction mediumand offer unique advantages in the design of a flat panel luminaire orprivacy screen 100. Such dots can include one or more diffusivematerials, for example, TiO2, in the form of an ink or paint

Turning to FIG. 3, a front schematic view of an embodiment of a privacyscreen 100 is shown. In this example, the privacy screen 100 includesturning facets 106. These turning facets are configured to extract lightpropagating within the panel 101 that is input into the panel 101 by thelight sources 103. The turning facets 106 may be embossed or machinedinto panel 101. The light sources 103 may comprise light emitting diodes(LEDs) or any other suitable light source including linear lightsources. As shown in the top edge view of the privacy screen 100 in FIG.4, light may propagate from the light sources 103 through the panel 101.Light propagating through the panel 101 can be trapped within the panel101 by total internal reflection (“TIR”) until it encounters lightturning facets 106. When the light encounters light turning facets 106,some of the light may be extracted from the transparent panel and beturned towards the front (or back) planar side making the privacy screen100 appear bright to a viewer. However, turning facets 106 or lightextraction features that are machined or embossed in the panel 101 maylimit the flexibility of the privacy screen 100 and cost more tomanufacture than light extraction features that are printed on the panel101. In some embodiments, light extraction dots (for example, asdescribed herein below) are disposed on one or more surfaces of thepanel 101 (shown in FIGS. 3 and 4) to enhance the light extractionproperties of the panel.

In the embodiment illustrated in FIG. 5, printed light extraction “dots”107 can be used on a privacy screen or luminaire as a flexible lightextraction feature that may enable a range of properties not possiblewith other light extraction methods. The dots 107 may be a mass ofmaterial that is added to the surface of the panel 101. The dots 107 mayvary in size and shape. Examples of suitable cross-sectional shapesinclude circles, ovals, generally curvilinear shapes, squares,rectangles, triangles, generally polygonal shapes, and irregular shapes.The dots 107 may each be about the same size or the dots can vary insize from one dot 107 to another.

As shown in FIGS. 5 and 6, dots 107 may be printed upon the front, backor both front and back surfaces of the panel 101 to extract light inputinto the panel 101 by light sources 103. Printed dots 107 can be used totailor the transparency and diffusion of the panel when in ambientlight, un-illuminated by a light source 103. Additionally, dots 107 canbe used to create uniform or non-uniform light extraction, with lightoutput on the front, back, or both sides of the panel 101. When thepanel 101 is illuminated by the light sources 103, the dots 107 can beused to direct light toward a viewer, effectively reducing the contrastof any image seen through the panel in order to act as a privacy screen.Also, through choices of materials, printing, and patterns, the lit andunlit properties of the panel 101 can be largely independentlycontrolled. For example, large dots 107 may be used to limit thetransmission through the panel 101 when the light sources 103 are dimmedor unlit. Similarly, a high concentration of smaller dots 107 can limitthe transmission through the panel 101 when the light sources 103 aredimmed or unlit. The large or small dots may comprise, for example,diffusive particles or opaque materials, and be configured thicker orwith a higher density to limit light transmission through the panel. Insome embodiments, a low concentration of smaller dots 107 may be used toallow transmission through the panel 101 when the light sources 103 aredimmed or unlit.

Still referring to FIGS. 5 and 6, printed dots 107 used as analternative to machine/embossed features offer a low cost, flexibledesign (e.g., controllable efficiency and uniformity), and flexibilityof panel 101 material (e.g., dots can be used on many substratesincluding glass and plastic). Additionally, the dots 107 can havediffusion characteristics and thus can mitigate the need for a topdiffuser. The dots 107 can be simple to manufacture, may require a lowcapital expenditure to manufacture, and are highly configurable. Forexample, the dots 107 may be printed onto the panel 101 by an ink jetprinter, screen printing techniques, or any other ink printer. The dotsmay also be rolled, splattered, or sprayed onto the panel 101. The dotsin any of the embodiments described herein can be formed by any of theseprocesses, unless specifically stated otherwise. The dots 107 may beprinted on both sides of the panel 101 to create a dual-faced lightextraction luminaire or privacy screen. In one example, a panel 101 mayhave a thickness of equal to greater than about one fourth of an inchfor a four foot wide panel.

Turning now to FIG. 7, a front schematic view of one embodiment of aprivacy screen 100 is shown. The privacy screen 100 includes at leastone light source 103 and a panel 101. Light extraction dots 107 aredisposed onto at least one side of the panel 101 to extract light thatis input into the panel 101 by the at least one light source 103. Asshown in FIG. 7, the dots 107 may be large enough and patterned suchthat objects placed behind the privacy screen 100 may be partiallyobscured by the dots 107 when the light source 103 is dimmed, or unlit.One or more characteristics of the dots 107 can affect light reflectedand/or transmitted through the panel 101. For example, the dots 107illustrated in FIG. 7 can be configured in various embodiments to have acertain diameter, thickness, pattern, composition including bindermaterials, diffusive particles, color reflective particles, and multiplelayers, as described in reference to FIGS. 8-18. Also, the total visualoptical effect of the panel 100 can be affected by one or more opticalelements (e.g., that also diffuse, reflect, or refract light) placedeither behind or in front of the panel 101 (with respect to a viewer),for example, as described in reference to FIGS. 19 and 20.

Another embodiment of a privacy screen comprising dots 107 is shown inFIG. 8. The dots 107 in FIG. 8 are smaller in diameter than thoseillustrated in FIG. 7, and are disposed in a pattern where the center ofthe dots are positioned closer together in a “finer” dot pattern. Thedots 107 and pattern can be designed to extract the same amount of lightas the larger dots in FIG. 7 when illuminated, but the dots in FIG. 8will be less visible at a distance. The fine dot pattern comprising alarger number of dots 107 than the coarse dot pattern illustrated inFIG. 7, and smaller dots 107, may obviate the need for a diffuser tocreate even illumination.

FIG. 9 illustrates another embodiment of a privacy screen 100 thatincludes a panel 101, a light source 103 positioned along the left andright sides of the privacy screen 100. In the embodiment, as well as theother embodiments described herein, the light source 103 canalternatively be disposed along one side, or along three or four side ofthe screen 100. The dots 107 in this embodiment are disposed on thepanel 101 in a pattern where the spacing between adjacent dots changesin relation to the distance to the light source 103. In this example thedistance between adjacent dots decreases as the distance from the lightsource 103 increases. Also, the size and pitch (e.g., the distancebetween dots) of the dots 107 changes (increases in this example) as thedistance from the light source 103 increases. Such a pattern can be usedto extract a uniform amount of light from the panel 101 even though thecenter portion of the panel is farther from the light source 103.Changing the composition of the dots 107 (e.g., the number and type ofdiffusive particles, the type of binder material) and/or theirconfiguration (e.g., two or more layers, disposed partly or wholly on anisolation layer) may also help extract more light from dots 107 locatedin the center of the display panel 107. In other embodiments, the dots107 may vary in size, shape, spacing and composition such that the dots107 affect the reflective and transmission characteristics of the panel101 when the privacy screen 100 is lit by the light source 103 and/orunder ambient light conditions. Printed dots provide more flexibility indesign and manufacture compared to alternatives—such as grooves, pits,and prismatic features.

Turning now to FIG. 10, an edge view of a privacy screen 100 is shown.The privacy screen 100 includes a light source 103, a panel 101, and adot 107. Light emitted by the light source 103 is trapped in the panel101 by total internal reflection until the TIR is frustrated by thelight encountering dot 107. The dot 107 has a refractive index greaterthan or equal to the refractive index of the transparent panel such thatsome of the light enters the dot 107 and is scattered, some of the lightbeing extracted. Some of the light scattered by the dot 107 is scatteredand/or reflected back into the panel 101. The light reflected orscattered back into the panel 101 will continue travelling along thepanel 101 if it enters the panel 101 at a lower angle that allows it topropagate in the panel 101 by TIR. Additionally, if the dot 107 ispartially transparent, some light may emerge through the other side ofthe dot 107, allowing for two side illumination from the panel 101.Light that is scattered into the panel 101 from the dot 107 that entersthe panel 101 at a higher angle will emerge from the panel 101 afterbreaking TIR. Accordingly, as illustrated in FIG. 11, a privacy screen100 may be configured for dual sided light extraction (on the frontplanar side and back planar side) when dots are printed on one or bothsides of the panel 101. In some embodiments, optical characteristics ofdots disposed the front and back sides differ, such that the appearanceof the panel differs when viewed from the front or back sides.

Turning now to FIG. 12, a close-up edge schematic view of a privacyscreen 100 is shown according to one embodiment. The privacy screen 100includes a panel 101 and a plurality of dots, FIG. 12 illustrating anexemplary single printed dot 107. The dot 107 includes a binder material109 and a plurality of diffusive particles 111. The diffusive particles111 can refract, reflect, and scatter light. Depending on theirconfiguration, such dots can appear transparent but diffuse, or they mayappear at least partially opaque. The dot 107 may extract light fromwithin the panel 101 when the refractive index of the binder material109 is equal to or greater than the refractive index of the panel 101.The diffusive particles 111 may extract light from within the bindermaterial when the refractive index of the diffusive particles is greaterthan the refractive index of the binder material 109. In one example,the diffusive particles 111 comprise a material having a high refractiveindex (e.g., >2). For example, the diffusive particles may comprisetitanium dioxide (“TiO₂”), or zinc oxide (“ZnO”). Varying the refractiveindex of the binder material 109 provides a degree of control over lightextraction that is independent of the size and shape of the lightextraction feature. For example, a large dot (covering a relativelylarge coverage area on the panel) extracts more light than small dot(having a relatively small coverage area on the panel). Light extractionfrom the panel 101 may also be controlled by disposing the dots indenser or more sparse configurations.

FIG. 13 illustrates another close up view of an embodiment of a panel101 that can have a plurality of light turning dots, illustrated here bya single dot 107. Dot 107 has a greater diffusive particle 111 densitythan the dot shown in FIG. 12. Higher diffusive particle 111 densitywill scatter more light back into the panel 101 and allow less light todiffuse through the dot 107. Variations in the characteristics ofdiffuser particles 111, including refractive index, will alter diffuserproperties. For example, diffuser particles 111 having a high refractiveindex will contribute to greater light scattering. In addition tovarying the refractive indexes of the binder material 109 and thediffusive particles 111, the light extraction properties of a dot mayalso be controlled by dot size and density. For example, large dotsextract more light than smaller dots. As shown in FIG. 14, a printingprocess can be used to control printed side 131 and panel side 133 lightextraction. The natural meniscus of a larger dot, larger ink volume, orlayered printing process can be used to control dot thickness andtherefore control light scattered through the dot 107. Thicker dots willextract less light on the printed side 131 and extract more light on thepanel side 133. Light extraction on each side of the panel 101 may becontrolled through printing dots on both sides. In some embodiments,dots having two or more different configurations of diffusive particlescan be printed on the same side of the panel 101, or on both sides.

Turning now to FIG. 15, an edge view of a privacy screen 100 is shown.The privacy screen 100 includes a panel 101 and a light source 103.Isolating layers 113 are disposed onto the panel 101. The isolatinglayers 113 may be disposed between a portion or all of a dot 107 and thepanel 101. As shown, dot 107 b is disposed upon an isolating layer 113,a portion of dot 107 c is disposed upon isolating layer 113, and anotherportion of dot 107 c is disposed upon panel 101. The isolating layers113 may have a refractive index that is less than the refractive indexof the panel 101 to prevent frustration of TIR by the dots 107. Forexample, when a dot is printed directly on the panel 101, both internallight from the light source 103 and external light impinging on thepanel 101 will interact with the dot 107. However, as shown, dot 107 bwill not interact with light traveling within the panel 101 because TIRwill not be frustrated by the low refractive index isolating layer 113.Additionally, external light impinging on dot 107 b from the dot printedside of the panel, or via the opposite side of the panel 101 may breakTIR at the interface between the dot and the panel.

The isolating layers 113 may be used to fully or partially shield theinternal light within the panel 101 from the light extracting dots 107b,c. Printed dots 107 provide a unique way to allow independent controlof lit and unlit light panel aesthetics when used with isolating layers103. Non-light extracting dots 107 c can be included in the design,which appear identical to light extracting dots to a viewer, but do notextract light or extract a smaller amount of light than light extractingdots. An isolating layer 113 having a lower refractive index under someor all of the dots will prevent light extraction at these locations.Dots may also be completely or partially shielded by the isolation layer113 to allow a light extraction pattern of variable dot area to bedesigned to appear uniform to a viewer of the screen 100. The isolatinglayers 113 may be printed on or bonded to the panel 101. In cases wherethe isolating layers are bonded to the panel 101, the isolation layermay include a low index adhesive, or a lower index adhesive may be usedto bond a separate isolation layer structure. In other embodiments,light extraction can be controlled in one or more dots by using lowerindex binders that extract less light, by using a lower index diffusermaterial(s), by varying the thickness of the dot, and/or by varying thediffuse material density.

FIG. 16 illustrates an embodiment of a privacy screen 100. The privacyscreen includes light extracting dots 107 a and non-light extractingdots 107 b. As shown, the light extraction dot pattern is non-uniform toextract more light away from the edge mounted light sources 103 in orderto create even illumination. However, additional non-light extractingdots 107 b can be added to create a uniform dot pattern, which isvisible when the panel 101 is not illuminated.

FIG. 17 illustrates an embodiment of a privacy screen 100. The privacyscreen includes light extracting dots 107. The light extracting dots 107include an outer layer 123 and an inner layer 121. The inner layer 121and/or outer layer 123 may be colored to add color when illuminated withwhite light. When the outer layer 123 is white and the inner layer 121is colored, the dots appear white to a viewer viewing the privacy screen100 from the same side as the dots 107 and the dots appear colored to aviewer viewing the privacy screen 100 from the other side. As shown inFIG. 18, dots may be patterned to appear different colors to a viewer.For example, dots 107 d may appear white to a viewer and dots 107 e mayappear green.

In another example, a dot 107 with an inner layer 121 and outer layer123 may extract a different color on each side of the panel. Forexample, a partially transparent dot 107 with a white inner layer 121and a green outer layer 123 will extract green on the dot side and aless green, whiter color into the panel and out the other side. An outerlayer 123 may reflect light incident from outside the privacy screen 100while the inner layer 121 may extract light of another color. In suchembodiments, the amount of light that is extracted on the dot side ofthe panel can depend on how much of the outer layer is in contact withthe panel surface, and/or how the thickness or opacity of the innerlayer (as these characteristics increase, more light will be reflectedfrom the dot within the panel towards the opposite side). Accordingly, aprivacy screen 100 can appear colored to a viewer looking through itfrom one side, while reflecting and/or extracting white light on theother side.

In other embodiments, white dots can be illuminated with colored light.In another embodiment (not shown), a privacy screen 100 could includelight extracting dots 107 with inner layers 121 and outer layers 123 onboth sides of the privacy screen 100. For example, dots 107 with whiteinner layers 121 could extract white light toward the back and dots 107on the back with green inner layers 121 could extract green light towardthe front.

FIGS. 19 and 20 illustrate edge views of privacy screens 100. Privacyscreens (or luminaires) configured as described above may be combinedwith a diffuser or reflector to further control the specularity ordirection of light output in specific applications. FIG. 19 illustratesan embodiment of a privacy screen 100 comprising a reflector 125configured to reflect light from the panel 101. The reflector 125 may bedisposed near the planar back surface of the panel 101 to reflect lightthat is emitted from the planar back surface through the panel 101 andout of the planar front surface. In some embodiments, the reflector 125may have a surface area that is similarly sized to the planar backsurface in order to reflect substantially all of the light emitted fromthe planar back surface back through the panel 101. In otherembodiments, the reflector 125 may be configured to reflect only aportion of the light emitted from the planar back surface back throughthe panel 101.

FIG. 20 illustrates an embodiment of a privacy screen 100 comprising adiffuser 127 configured to diffuse light that is extracted from thepanel 101. The diffuser 127 may be disposed near one or more planarsurfaces of the panel 101 in order to diffuse light that is emitted fromthe one or more surfaces. For example, in one embodiment, the diffuser127 may be disposed over the planar back surface of the panel 101 todiffuse light that is emitted from the planar back surface. In someembodiments, the diffuser 127 may have a surface area that is similarlysized to a planar surface of the panel 101 in order to diffusesubstantially all of the light emitted from the planar surface. In otherembodiments, the diffuser 127 may be configured to diffuse only aportion of the light emitted from a planar surface of the panel 101.

FIG. 21 is an edge view of an embodiment of a privacy screen 2100 thatcomprises a light source 103 disposed on one or more sides of a lightguide panel 101 (shown here on one side) to provide light to a lightguide panel 101. The light extraction dots (features) 107 can be formed(e.g., printed) on a film (or a sheet) 2102. The film 2102 can beattached to a planar front surface 2106 or back surface 2108 of thelight guide panel 101. In some embodiments, a first film 2102 with dots107 (“dot printed film”) formed thereon is attached to the front surface2106 and a second film with dots formed thereon is attached to the backsurface 2108 (not shown) of the panel 101. The dots 107 illustrated inFIG. 21 can have any of the characteristics of the light extraction dotsdescribed herein, including for example size, composition, andreflective, transmissive, diffusive, and refractive opticalcharacteristics. In some embodiments, a dot printed film 2102 can beattached to the panel 101 in a variety of suitable ways, including butnot limited to a heat fusing process, or a sheet or adhesive 2104 (forexample, a low index adhesive). In some embodiments, an adhesive film2104 is disposed between and bonds the panel 101 and the dot printedfilm 2102.

To manufacture some embodiments, the dots 107 can be first printed onthe film 2102. Subsequently the film 2102 is bonded to the light guidepanel 101 using an adhesive 2104. In some embodiments, bonding can bevia a pressure sensitive adhesive (“PSA”) 2104 that has a refractiveindex equal or lower than the refractive index of the light guidingpanel 101. The dot printed film 2102 in turn has a refractive indexequal or lower than the adhesive 2104. In other embodiments, the film2102 can be directly bonded to the panel 101 using materials that fusetogether under heat and/or pressure, for example a copolyester like PETG(glycol-modified polyethylene terephthalate) that is a clear amorphousthermoplastic. Dot printed films 2102 can be printed separately from thelight panel 101, such as using a low cost litho process, which canreduce manufacturing costs and also separate product manufacturingbetween suppliers. In some embodiments, two or more films comprisingprinted dots can be bonded to the light panel in layers, allowing use oflayering techniques described in the application relating to isolationlayers and multi-layer dots, for example, in FIGS. 15 and 17.

FIG. 22 is a block diagram depicting a method 2200 of manufacturing alighting apparatus, according to one embodiment. Method 2200 includesthe steps of optically coupling a light source to an at least partiallytransparent panel comprising a planar front surface and a planar backsurface, the panel is disposed in conjunction with the light source suchthat light from the light source is input into at least one edge of thepanel and guided therein 2202 and printing a plurality of lightextraction features on the panel front surface, the plurality of lightextraction features configured to reflect light incident on the panelfront surface and extract light from the light source through the panelback surface 2204.

FIG. 23 is a block diagram depicting a method 2300 of manufacturing alighting apparatus, according to one embodiment. Method 2300 includesthe steps of printing a plurality of light extraction dots onto a sheet2302 and bonding the sheet to a surface of an at least partiallytransparent light panel having a front and back surface such that thesheet is disposed between the plurality of light extraction dots and thepanel 2304. In method 2300, the bonding may comprise attaching the sheetto the panel using an adhesive having an equal or lower refractive indexthan the refractive index of the panel such that the light extractiondots are operable to extract light propagating between the panel frontand back surface.

The foregoing description details certain embodiments of the invention.It will be appreciated, however, that no matter how detailed theforegoing appears in text, the invention can be practiced in many ways.As is also stated above, it should be noted that the use of particularterminology when describing certain features or aspects of the inventionshould not be taken to imply that the terminology is being re-definedherein to be restricted to including any specific characteristics of thefeatures or aspects of the invention with which that terminology isassociated. The scope of the invention should therefore be construed inaccordance with the appended claims and any equivalents thereof.

1. A lighting apparatus, comprising: an at least partially transparentpanel including a planar front surface and a planar back surface, thepanel configured to receive light provided from a light source throughan edge of the panel and propagate the light within the panel; and afilm positioned on the back surface, the film having a plurality oflight extraction dots disposed thereon, the plurality of lightextraction dots configured to extract light propagating in the panelthrough the front surface.
 2. The apparatus of claim 1, furthercomprising a light source.
 3. The apparatus of claim 2, wherein thelight source is configured to switch between at least a first mode and asecond mode, the light source emitting more light in the second modethan in the first mode.
 4. The apparatus of claim 3, wherein theplurality of light extraction dots are configured to extract more lightin the second mode than in the first mode such that the visibilitythrough the transparent panel is greater in the first mode than in thesecond mode.
 5. The apparatus of claim 1, wherein at least one of theplurality of light extraction dots includes an inner layer disposedproximate to the transparent panel and an outer layer disposed at leastpartially on the inner layer, wherein the outer layer includes a firstcolored material that reflects ambient light of a first color and theinner layer includes a second colored material that reflects light,propagating within the panel, of a second color.
 6. The apparatus ofclaim 1, further comprising an adhesive disposed between the film andthe panel for bonding the film to the panel.
 7. The apparatus of claim6, wherein the adhesive is a pressure sensitive adhesive.
 8. Theapparatus of claim 1, wherein the film includes a plurality ofnon-extraction features.
 9. The apparatus of claim 8, wherein the filmincludes an isolation layer disposed between the plurality ofnon-extraction features and the back surface, the plurality ofnon-extraction features and the plurality of light extraction dotsdisposed in a uniform pattern.
 10. The apparatus of claim 9, wherein theplurality of non-extraction features includes one or more dots.
 11. Amethod of manufacturing a lighting apparatus, comprising: printing aplurality of light extraction dots onto a sheet; and bonding the sheetto a surface of an at least partially transparent light panel having afront and back surface.
 12. The method of claim 11, wherein the sheet isbonded to the back surface and wherein the plurality of light extractiondots is configured to extract light propagating in the panel through thefront surface.
 13. The method of claim 11, wherein the bonding includesattaching the sheet to the panel using an adhesive having an equal orlower refractive index than the refractive index of the panel.
 14. Themethod of claim 11, wherein the bonding includes attaching the sheet tothe panel using heat and/or pressure.
 15. The method of claim 11,further comprising optically coupling at least one light source to anedge of the panel.
 16. The method of claim 15, wherein the light sourceis configured to switch between at least a first mode and a second mode,the light source emitting more light in the second mode than in thefirst mode.
 17. The method of claim 16, wherein the plurality of lightextraction dots are configured to extract more light in the second modethan in the first mode such that the visibility through the panel isgreater in the first mode than in the second mode.
 18. The method ofclaim 11, further comprising disposing a plurality of non-extractionfeatures onto the sheet.
 19. The method of claim 18, wherein thenon-extraction features include one or more dots.
 20. The method ofclaim 19, wherein the non-extraction features are printed onto thesheet.
 21. A method of manufacturing a lighting apparatus, comprising:optically coupling a light source to an at least partially transparentpanel comprising a planar back surface and a planar front surface suchthat light from the light source is input into at least one edge of thepanel and guided therein; and placing a plurality of light extractionfeatures on the back surface, the plurality of light extraction featuresconfigured extract light from the light source through the frontsurface.
 22. The method of claim 21, wherein the plurality of lightextraction features are further configured to reflect ambient lightincident on the back surface.
 23. The method of claim 21, whereinplacing the plurality of light extraction features comprises printingthe plurality of light extraction features onto the panel using an inkjet printer.
 24. The method of claim 21, wherein placing the pluralityof light extraction features on the back surface comprises screenprinting.
 25. The method of claim 21, wherein the plurality of lightextraction features comprises one or more light extraction dots.
 26. Amethod of screening by decreasing the visibility through a panel,comprising: positioning an at least partially transparent panelcomprising a planar first surface and a planar second surface in alocation to screen an object or an area, the panel comprising aplurality of light extraction dots disposed on the panel, the lightextraction dots configured to extract light propagating within the panelthrough the first surface of the panel; providing light into the panelat a first illumination level; and providing light into the panel at asecond illumination level, the second illumination level being greaterthan the first illumination level such that more light is extractedthrough the first surface of the panel at the second illumination levelthan at first illumination level lowering the visibility through thepanel as viewed through the first surface of the panel.
 27. The methodof claim 26, wherein the at least one light extraction dot includes aninner layer disposed proximate to the transparent panel and an outerlayer disposed at least partially on the inner layer, wherein the outerlayer includes a first colored material that reflects ambient light of afirst color and the inner layer includes a second colored material thatreflects light, propagating within the panel, of a second color.